A phosphanyl-substituted benzo-1,3,2-dioxaborol as ambiphilic bifunctional Lewis donor-acceptor unit

Abstract

Condensation of 3-[(diphenylphosphanyl)methyl]benzene-1,2-diol (1) with phenyl boronic acid gave a phosphane-functionalised benzo-1,3,2-dioxaborol 3. The ability of this species to act as a Lewis base through the P-centered donor and as a Lewis acid through the B-centered acceptor sites was demonstrated by the reactions with (cod)PdCl2 and some nitrogen donors (4-dimethylaminopyridine, diaza-[2.2.2]-bicyclooctane, pyridine). These reactions yielded either palladium-phosphane complexes or amine-borane adducts that were characterised by spectroscopic data and, in some cases, by single-crystal X-ray diffraction studies. Reactions of a Pd complex of the phosphane-functionalised benzo-1,3,2-di-oxaborol 3 with dabco, or of the dmap adduct of 3 with (cod)-PdCl2, gave materials that were characterised by analytical data and solid-state NMR spectroscopic data as triple Lewis acid/base complexes and that contain both P→Pd and B←N dative bonds. Even though these adducts were unstable in solution, the results of these experiments demonstrate the ability of 3 to act as a bifunctional donor/acceptor ligand, which is of potential use as a building block for main chain organometallic polymers or multimetallic complexes. © Wiley-VCH Verlag GmbH & Co. KGaA, 2008.